The birthday card Musk gave Gwynne in December 1995 reads: “Happy birthday Jennifer (aka Boo Boo). Love, Elon.”
The signed card is expected to sell for more than $10,000 when bidding ends Wednesday.
Gwynne told DailyMail.com that “Boo Boo” was what Musk called her when teasing her playfully.
Another popular item, a dollar bill signed by Musk, has a top bid of $7,604 as of early Monday morning. A photograph of Musk sitting at the computer has solicited 26 bids — with the highest bidder willing to fork over $1,355.
Gwynne and Musk started dating at the Philadelphia-based Ivy League school in the fall of 1994 while they both lived in the same dormitory as resident advisers.
One photo in the collection being put on the block by Boston-based RR Auction shows Musk wearing a “Judge Dredd” T-shirt — which pays homage to the comic book character that inspired the movie starring Sylvester Stallone.
In another photo, a smiling Musk is seen lying down on the floor with his hands behind his head while Gwynne snaps a picture of him as he looks into the camera with his feet apparently on her lap.
Another photo shows Musk displaying a tender side as he lies on a couch while embracing Gwynne, who is cuddling with him.
Musk is also seen sightseeing at Niagara Falls and hiking in San Francisco. Another photo shows him dining out with four other classmates at a local restaurant.
Gwynne, 48, told DailyMail.com that she is selling the photos in order to help fund her stepson’s college tuition.
Gwynne said that Musk was ambitious and idealistic. She “always knew” that he would “go places,” she said.
“He was very intense, very focused on his studies,” she said.
“Back then he was always talking about electric cars… he was definitely going somewhere.”
“He just saw school as a stepping stone.”
She told DailyMail.com that while their relationship was “sweet,” Musk would withhold “PDA” — public displays of affection.
“His shy nature attracted me at first,” Gwynne said, adding that “he used to be my type.”
She added: “‘We were physical when we needed to be… but there wasn’t any hand-holding or anything like that.”
“He liked to be together,” Gwynne said.
“He just liked having someone there with him, someone to support him.”
She is also auctioning off a 14-karat gold necklace that Musk bought her while they were visiting his mother in Toronto.
Gwynne told DailyMail.com that he initially intended for the necklace to be a Christmas gift, but they decided that it would instead be a birthday present.
The relationship ended when Musk moved to Palo Alto, Calif. after that semester. Gwynne said she visited him once out West, but they decided to end the relationship.
“If we weren’t physically together it was a problem because he’s not good on the phone,” Gwynne recalled.
“He said, ‘It’s a waste of time’.”
‘It was hard, it was not what a 20-year-old woman wanted to hear. I was totally in love with him,’ she said.